The limited diagnostic and prognostic utility of brief cognitive screening tools in acute stroke

Guidelines recommend cognitive screening post-stroke, but there is no consensus on approach. Given the dynamic nature of cognition following stroke, acute screening should both detect prevalent issues (diagnosis) and predict persisting problems (prognosis). We describe the diagnostic and prognostic utility of brief cognitive screening tools.

Patients were screened on admission with stroke using 12 modified screening tests: 10 and 4 question Abbreviated Mental Test, Cog-4, Clock Drawing test (CDT), Cognitive Impairment Test, informal bedside assessment, General Practitioner Assessment of Cognition, Minicog, Short Form Montreal Cognitive Assessment, Six-Item Screener (SIS), Harmonised Vascular Cognitive Impairment battery and 4-A's Test. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value were calculated against a Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition adjudicated reference standard of neurocognitive disorders. Test accuracy was compared using area under the receiver operator characteristic curves.

Of 335 patients, 54 (16.1%) had pre-stroke neurocognitive disorder, 79 (23.6%) had 18-month neurocognitive disorder. Ten of 12 screening tests were more specific than sensitive. Informal bedside assessment had highest specificity (96%), but low sensitivity (9%); CDT had highest sensitivity (80%) but low specificity (33%). Negative predictive value ranged from 77% to 87%, PPV ranged from 27% to 54%. Area under the receiver operator characteristic curve ranged 0.53 (informal bedside assessment) to 0.69 (SIS).

In the acute setting, where the intention of screening is often to triage those who need further assessment, the pattern of high specificity at the expense of sensitivity is the opposite of what is desired.

Brief cognitive screening tools, used in isolation, may not be suitable for assessment in acute stroke settings.